Pneumatic apparatus for measuring fluid pressure



Oct 1952 J. c. THORESEN PNEUMATIC APPARATUS FOR MEASURING FLUID PRESSURE 2 SHEETS- SHEET l Filed Sept. l, 1945 INVENTOR B/0///V 6'. THO/e555 ATTORNEY Oct. 21, 1952 c, THORESEN 2,614,424

PNEUMATIC APPARATUS FOR MEASURING FLUID PRESSURE Filed Spt. l, 1945 A 2 SHEETSSHEET 2 INVENTOR /0///\/ c rmefmv BY 7 8, C. d

ATTORNEY Patented Oct. 21, 1952 PNEUMATIC APPARATUS FOltMEASURING FLUID PRESSURE John C. Thoresen, Warwick, R. 1;, assignor to Builders 'Iron Foundry, Providence, R. I., acorporation of Rhode Island Application September 1, 1945, 'Serial No.e14,042

This'inventio'n' relates to the measurement of values of a variable condition and more particu-' larly to pneumatic apparatus for measuring variable magnitudes and transmitting the valuesthereof to a desired point.

- Anobject of the invention is the provision of a novel pneumatic meter of relatively simple con-' struction for the efiicient measurement and transmission of variable values.

The invention provides more specifically a novel measuring apparatus wherein forces corresponding to variations in the magnitude of a condition are applied to an arm of a lever system and are balanced by variations in force applied to'another arm of the system, which latter variationsare in turn communicated to a measuring instrument at any desired point for indicating the values of the condition under measurement.

Another feature of the invention resides in novel provisions for the measurement of the rate of flow of a fluid in response to a diiferential pressure varying as the square of said flow rate. In that connection, the invention provides means for creating, in response to said differential pressure, an-air pressure having alinear relation'to the rate of flow of said fluid.

Other features of the invention will be hereinafter described and claimed.

-In the accompanying drawings:

Fig. 1 is a diagrammatic view illustrating an embodiment of the invention applied to the telemetering'of the rate of flow of a liquid,

'Fig. '2 shows an embodiment of the invention for telemetering the level of a liquid.

Fig. 3 'sho'ws' an embodiment of the invention applied to the telemetering of the loss of head of a liquid due to passage through a given medium.

Fig. 4 is a view in front elevation of apparatus for recording the telemetered values.

Referring to the drawings, there is shown in Fig. 1 a conduit II] having a Venturi section II for'the passage of a liquid whose flow rate is to be measured. I

Mounted ina housing I2 is a flexible diaphragm I 3;"which'divides the interior of said'housing l2 into chambers I4 and IS. 'The latter are connected' to high and low pressure points in the 5 Claims. (Cl. 73-213) receiving knife-edge bearing means I9 on the lever I9.

At its opposite end the lever I9 is flattened to provide a vane portion 2| which lies in proximity to a port 22' for the emergence of air through a bleeder nozzle 22. Suspended from said lever I9 ata point between the fulcrum I9 and vane portion 2I is a well 23, which is con-' nected by a; flexible tubing 26 with a stationary well 25; or other suitable manometric liquid. A

Air under pressure is supplied to a passage 26 in a manifold 2'! shown abovethe stationarywell 25;"which passage 26 communicates with said well through a channel 21, and with the bleeder' supplied to said manifold through apparatus of Well-known type comprising a filter and moisture Venturisection by the respective conduits I6 and gauge 3|, pinhole orifice 32, and conduit 33. pressure gauge 34, which may be of conventional construction, is also connected to the passage 26 by a suitable conduit 35. The conduits 33 and 35 may, if desired, extend through very substantial distances from the manifold 21 and are hence indicated by broken lines.

The upper portion of the well 23' is in commu nication with the atmosphere through suitable openings 23".

When no fluid is flowing through the conduit I 0, no differential pressure is applied to the. diaphragm I3. At that time the mercury in the wells 23"and 25 is at a common level, indicated by the dottedline 36. Under that condition, the

weight'of the liquid in the well 23 acts upon the lever I9 so that the vane 2| is in its lowermost position beneath the air escape port 22. The pin hole orifice is of such small diameter with respect to that of the port 22 that when said vane 2| is in said lowermost position the pressure in the,

manifold system is practically zero. For example, a diameter of about :010" of said pin hole orifice has been found suitable when the diameter of the port 22 is .04" but these dimensions are not critical.,, As liquid flows through the conduit II) adififerential pressure is applied to the diaphragm, I3,'.

forcing said diaphragm downwardly andthereby exerting'a downward pull uponthe lever arm to the left of the fulcrum I9.. The vane 2| is thus moved upwardly toward the port 22', obstructingthe flow of air therethrough, with consequent building up of pressure in the manifold .21. This. pressure acts downwardly upon the mercury iii the well 25 and forces mercury therefrominto Said wells 23 and 25 contain mercury the moment'of forcerapplied to said lever about said fulcrum-by the aforementioned differential pressure. At that time the lever system is balanced. The air pressure required to continue the balance is maintained in .the manifold sys-, tem and is indicated by the pressure gauge 34.

It will be noted that the moment which counteracts the efiect of variations imdlfier. ential pressure upon the lever I9 is itself variedsimply by change in the amount of liquid in the well 23, without change in the distance from.

the fulcrum I9 to the point of suspension of said well. Rebalancing of the lever system is thus obtained without variation in the length of theefiective lever arm.

Because of the Venturi law, the pressure differ: ential created across the: diaphragm I3 varies as the square of therateof fiow=of the liquid inthe Hence, the .pull' on the diaphragm;

conduit .Iil: andthe corresponding moment M1 applied by stemnI8. tothe -lever- I9-'will -varyyas the square Ofz'llhGrlEtllB of flow. The stationary well-25 is so shapedithat the volum of liquid displaced intothe floating-well 23 will vary asthe square of the total pressure required inthe manifold to maine tain-balance. As aresult; the momentMz exerted upon-.the lever by the liquidforced into thewell- 23 will vary as :the square of the air pressure At-a stateof balance; the. I moments lvh and M2 are equal, and it will henceinthe manifold 2'].

be apparentrthat the manifold pressure ,varies linearly} in correspondencewith the rate of'xfiow of theliquidthrough the conduit I and Venturi section I I. The readings of the gauge 34 thus are proportionalitosaid rate of-flow.

p In. otherwords, the moment M1=DAa,, where. D. is .thedifferential pressure; A is v the effective area .of the diaphragm, and a is the distance-between points I8 and I9. The moment M z=Wb where W is the weight of liquid. in the well/.23-

in' excess of that in. said well when the air pressure-in the manifold 21 is substantially, zero, and b is the distance from fulcrum I9 to :the point of suspension of .said well. When M1 =M2,

(l) i DAdiWb As" above'noted, D. is proportional to the squareof "the .flowrate. V), .while W is proportional tothe. squareofitheair pressure (P) necessarygto:

eifectbalancing of theleversystem. Hence;

Substituting theseivalues of.D' and-W- in the,

above noted equation- (l) there. results (2)1" V; C'Aa'=P C'b Since G; A. a, .C, andfb .are constantsit is apparent'thatV is proportional tol? and..that V varies as P. sothatthe airpressure necessary to maintain balance varies linearly. as the ,flow v rate under measurement.

The floating .well..23 may. if. desired. bead; justablymounted'on the lever I9, .as. throughe. sleeve '31 providedjwitha set screw-3l' for fastening the sleeve 31'and.well.23 in any positionv ofadjustment. Thus the moment M2 may .be varied for any given maximum pressure in the; manifold by moving th'e'g point .of. support o: said floating- 2,614,424 1 .I; .3" it along the lever I9.

In Fig. 2..apparatus embodying my invention is shown applied'to the measurement of the level of a liquid 40 in a tank H. The apparatus is the same :asgthat ofFig. 1 except that the upper .diaphragm'chamberl l is in communication with thebottorzi portionof tank 4I through a pipe 42, while the chamber I5 is open to atmosphere through opening 43; Also the stationary well 25; is straight-sided, so that there is a linear relation between the output air pressure and the amount of liquid displaced from saidwel-l ;25., to the-floating-well. 23.

proportional-tothe level of; the-liquid :in .the tank 4I, it will be apparent that 'the air;pressure necessary to maintain'balanceiis alsoeproportional to said :level.

In Fig. 3, the-apparatusis thesame as LinFigz: 2, except that the diaphragm chamberqliis'cone. nected by conduit 43 to liquid; above a ;-filter;;bed it while the diaphragm-chamber I 5 is connected by conduit, 45..to liquid inthe pipe 46 below;= said: filter bed. Thus. theediaphragm I3 'is subjected;

to va-differential pressure which varies-zlinearly;

as the. loss of head in: the; filter bed-:and-the: air? pressure. necessary-to. eifect balance of the. lever: system likewise. varies linearly as ,;saidloss :5 of

head. a

In all of theembodiments above described-{it will be. apparent that the gaug 3 4 which measuresjthe balancing air pressure may .be graduated. in suitable. units forindicatingthe .valuesof the.

condition .to which said-airpressure-impropore;

tional. Where arecord of ,saidrcondition -or. totalization ofv its values, is desi-redfithenpres sure;

gauge 34 may'be'replacedby apparatuscofrwell known type. for accomplishing such results. Such apparatus may, forexamplefibeo-f thevformi manufactured by. applicantsassignee and; sold under the trade-markFlo-watch-gwhich apparatusis illustrated in publications ;of -said as si gi iee;. such' as Bulletins Nos. 284, and 3 1 8B published in 1936. and 19%, respectively- Such-- apparatus, which is in substantial use, is-indicatedin 4 of .the. present application; .incIuding-a pen arm Bllfor recordingvalues of a variable conditiomona. chart 5i, andzapointer 52i1for indicating :said. values on a scale 53. A bellows responds to air pressure received through conduit 55=fromtheg manifold 21 to operatea linkr56 and::thereby';t0 transmit movement to said pen-armiand pointemi so that the latter arepoperatedsto difierentipo sitions, just as they are actuated byiatratemam' in the standard Flo-Watch. Operatiomofj'a totalizing mechanism (not shown); whichjiforms part ofsaidFlo-Watch'isalso effected-ltlirough: parts connected to-the: operating me'ans-:for:;sa-id. pen arm in the same manneraaslin the standard instrument, y Y

The. terms and expressions which-I ghave .Lem: ployed are used-,as-terms-of descriptionrandin'ot of limitation, and -I have1 no-intention; in the useioi such terms and; expressionsy of {excluding- 1 any equivalents =of the :features shown-and described or, -portions.-,; thereof butirecognizegthatnvarlous And sincerth'e force applied to .thedever; I9 through thediaphragm': I3T'is.

modifications are possible within the scope of the invention claimed.

I claim:

1. Apparatus for measuring a variable magnitude, said apparatus comprising a lever, means for applying to said lever a force variable with changes in said magnitude, a receptacle adapted to contain a quantity of liquid and supported pendently by said lever for applying the weight of said liquid to said lever in opposition to the first-mentioned force, a reservoir for a liquid, flexible liquid-conduit means connecting said reservoir with said receptacle, and pressure means comprising a conduit and a nozzle having an outlet port connected to said conduit, means movable with said lever in response to variations in said force for variably obstructing passage of fluid through said port, and means connecting said conduit with said reservoir to subject the liquid therein to varying pressures in response to movement of said obstructing means to thereby effect balancing of said lever through variation in the weight of liquid in said receptacle.

2. Apparatus for measuring a variable magnitude, said apparatus comprising a lever, means for applying to said lever a force variable with changes in said magnitude, a, receptacle adapted to contain a quantity of liquid and supported pendently by said lever for applying the Weight of said liquid to said lever in opposition to the firstmentioned force, a reservoir for a liquid, flexible liquid-conduit means connecting said reservoir with said receptacle, and pressure means comprising a conduit and a nozzle having an outlet port connected to said conduit, means movable with said lever in response to variations in said force for variably obstructing passage of fluid through said port, means connecting said conduit with said reservoir to subject the liquid therein to varying pressures in response to movement of said obstructing means to thereby effect balancing of said lever through variation of the weight of liquid in said receptacle, said connecting means having a passage adapted for connection to a measuring means for obtaining a measurement of the fluid pressure required for balancing of said lever.

3. Apparatus for measuring the rate of flow of a liquid, said apparatus comprising a lever, means for applying to said lever a force corresponding with values of a differential pressure varying as the square of said flow rate, a receptacle adapted to contain a quantity of liquid and supported pendently by said lever for applying the weight of said liquid thereto in opposition to said force, a reservoir for a liquid, flexible conduit means connecting said reservoir and said receptacle, and fluid pressure means responsive to changes in said difierential pressure for applying pressure to the liquid in said reservoir for effecting flow of liquid from said reservoir to said receptacle for balancing said lever while the effective moment arm of said weight remains substantially unchanged,

said reservoir being so shaped that the amount of liquid passing therefrom to said receptacle varies as the square of the pressure applied to said liquid in said reservoir.

4. Apparatus for transmitting to a desired point a fluid pressure varying linearly as the rate of flow of a liquid, said apparatus comprising a lever, means for applying to said lever a force varying as the square of said flow rate, a liquid-containing fluid pressure chamber, means responsive to movement of said lever under variations in said force for varying the fluid pressure in said chamber, a receptacle supported pendently by said lever and secured thereto for maintaining a substantially fixed moment arm regardless of variations in said flow rate, means for transferring liquid from said chamber to said receptacle under the influence of the fluid pressure in said chamber for applying a correspondingforce to said lever through a substantially unchanging moment arm, said chamber being so shaped that the amount of liquid transferred therefrom to said receptacle varies asthe square of said fluid pressure, and pressure-responsive measuring means connected to said chamber.

5. Apparatus for measuring the rate of flow of a liquid, said apparatus comprising a lever, means for applying to said lever a force varying as the square of said flow rate, a fluid pressure chamber, means responsive to movement of said lever under variations in said force for varying the fluid pressure in said chamber, a liquid reservoir including said chamber and having an outlet opening. said reservoir being so shaped that liquid passes through said opening in amounts proportional to the square of the fluid pressure in said chamber, and a receptacle in communication with said outlet opening for receiving liquid therefrom and supported pendently by said lever for balancing the latter through a substantially unchanging moment arm.

JOHN C. THORESEN.

REFERENCES CITED The followingreferences are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,191,415 Gibson July 18, 1916 1,585,170 Roucka May 18, 1926 1,638,100 Roucka Aug. 9, 1927 1,638,101 Roucka Aug. 9, 1927 1,878,179 Rawling Sept. 20, 1932 1,972,054 Moller Aug. 28, 1934 2,217,642 Luhrs Oct. 8, 1940 2,257,577 Rosenberger Sept. 30, 1941 2,325,714 Stover Aug. 3, 1943 2,354,423 Rosenberger July 25, 1944 2,371,253 Moore Mar. 13, 1945 2,380,177 Hicks July 10, 1945 

